U.S. Pat. No. 4,454,260 describes a fluid stable suspension of water soluble polymer consisting of 40-140 parts of water soluble polymer dispersed in 100 parts of a liquid hydrocarbon medium to which 0.1-5 parts per 100 parts of hydrocarbon is added an alkali or alkaline earth metal salt of 6-33 carbon fatty acid as thickener. Other additives which are also specified for the suspension of this prior art include 0.1-10 parts of water, 0.1-50 parts of 1-12 carbon aliphatic alcohol and/or 0.1-50 parts of 2-12 carbon aliphatic diol per 100 parts of water soluble polymer.
The present invention differs from this prior art in the following regards:
A) The present invention employs the fatty acid in neat form and not in its salt form.
B) The present invention employs the fatty acid as liquid carrier for the suspension and not the thickening agent.
C) The present invention employs a proportion of fatty acid as the major ingredient, in excess of 40 wt. % of the suspension or greater than 100 parts of fatty acid per 100 parts of polymer, rather than a low proportion of 0.1-5 parts per 100 parts of polymer as given in the prior art of U.S. Pat. No. 4,454,260.
D) The present invention does not employ or require the use of aliphatic alcohol or water.
It is thus seen that the present invention differs substantially in composition and intent compared to the above prior art use of CMC and fatty acid in a fluidized suspension. The present invention thus could not have been anticipated from the prior art.
Prior art industrial use of CMC as a paper coatings thickener typically has not employed the direct addition of this thickening agent in its dry form to a paper coating formulation because in the case where dry powdered CMC is added directly to a paper coating formulation, severe lumping of the polymer is observed. Most prior industrial use of CMC as a paper coatings thickener has thus required the CMC to first be dissolved in water prior to its addition, in an aqueous solution form, to the paper coating formulation. However, this latter procedure suffers limitations in that it is laborious and time-consuming, and the highly viscous aqueous CMC solutions are difficult to prepare, store and handle. During the prior art procedure of adding powdered CMC to water to prepare aqueous solutions, CMC dust is often liberated. This can accumulate on floors where in the presence of water slipping hazards develop.
Another problem that is encountered with prior art use of CMC is that often during the course of preparation of CMC aqueous solutions, numerous undissolved gel lumps are formed due to the tendency of CMC to lump when added to dissolution water. These gel lumps then must either be stirred for a prolonged period of time in order to dissolve or must be filtered from the CMC solution before addition to the paper coating. Special mixing equipment may be required in order to prepare concentrated CMC solutions in water due to the high viscosity nature of these solutions.
Thus, the prior art use of CMC as a paper coatings thickener represented a difficult-to-use polymeric thickening agent. Therefore, it is evident that an improvement over the prior art use of CMC as a thickener for paper coatings would be useful and desired in the industry. The present invention, a fluid pourable suspension of CMC in fatty acid liquid organic media, has been found to offer a significant improvement over prior art handling and performance of CMC for paper coatings thickening application.